Method of producing tanning compositions from waste sulfite-cellulose liquor.



carton,

JOHANNES J. GROSS, OF HAMBURG, GERMANY.

METHOD OF PRODUCING TANNING- .COM P OSITIONS FROM WASTE SULFITE-CELLU'LOSE Patented Sept. 28, 1915.

LIQUOR.

1 ,154752 Specification of Letters Patent. No Drawing.

To all whom it may concern:

Be it known that I, JoHANNEs J. GRoss, a subject ofthe King of Prussia, and resident of Hamburg, Germany, have invented certain new and useful Improvements in Methods of Producing Tanning Compositions from Waste Sulfite-Cellulose Liquor, of which the following is a specification.

This invention relates toan improved method of producing tanning compositions from waste sulfite-cellulose liquor, which is distinguished from the known art by the tanning composition gained having essentially higher contents ofefficacious tanning matters. Whereas the proportion of the contents of tanning matters to non-tanning matters is about 1: 1 with the known sulfitecellulose employed as tanning compositions, this proportion is about 2:1 with the improved tanning composition, that is considerably higher. Furthermore the contents of mineral agents in the new product are very low.

According to the invention, the waste sulfite-cellulose liquor is treated in hot condition with hydrochloric acid (H01) and sulfuric acid (H SOQ whereupon the lime still present therein is eliminated by an addition of potassium monochromate (K CrO The product gained is then concentrated to about 20 B., then cooled with an admission of air, and the precipitates then falling arefiltered off, whereupon the remaining waste liquor is concentrated to any desired consistency.

It is-already known to treat waste sulfitecellulose liquor with strong mineral acids P (HCl) and sulfuric acid (H SO,,). Thereby,

under heat. The present invention is distinguished therefrom by the simultaneous emloyment of concentrated hydrochloric acid comparatively low contents of non-tanning matters, that is superfluous ingredients in the finished product are obtained, this resulting apparently from the fact that, while the hydrochloric acid decomposes the sulfites (SO Ca) and oxysulfites, of the lime, the

simultaneous presence of sulfuric acid (H SO converts the latter into insoluble sulfate of lime (CaSOQ. The latter, now precipitating, causes at the same time organic substances, which have been converted into greasy ingredients by the vigorous action of the hydrochloric acid (H01), to pre-' cipitate. ltis further known, to add chro- A pplication filed November 7, 1913. Serial No. 799,678.

mium compounds (Cr, salts) to waste sulfitB-CGllIflOSG liquor for .obtaining tannates of chromium, which possess tanning qualities. The method of the present invention works with chromates (Cr 1%) in such a way that the finished product contains practically no chromium compounds, but the chromate serves only for precipitating the lime as in soluble calcium chromate (CrO Ga).

The improved method is put into practice as follows: The waste sulfite-cellulose liquor is in a warm state mixed with pure concentrated hydrochloric acid (HCl) and ordinary sulfuric acid (H SO while being intimately stirred, and the mixture is boiled for some time. Thereupon, to the hot mixture a small addition of chromate of potassium (K CrO is made. The mixture thus obtained is allowed to stand for a certain time for precipitation, which can be accelerated by cooling. The clear product gained is Tanning matters, about 32% Non-tanning matters, about 18% Water, about 50% The simultaneous employment of hydrochloric acid (HCl) and sulfuric acid (H under heat has the advantage that hydrochloric acid (HCI) under heat acts in such a way that tanning matters, which can be absorbed by the skin, are formed of the non-tanning matters. Only by this fact, the.

strikingly high contents of tanning matters, in respect of the sulfite liquors hitherto employed for tanning, can be explained. The sulfuric acid (H SO precipitates the lime as calcium sulfate (CaSOQ, while the still present particles of lime are converted by the addition of potassium chromate K CrO into insoluble chromate of lime (CaCrOQ, which can be filtered off. A trifling excess of potassium chromate (Kr CrO would not unfavorably influence "the quality of the composition. A further advantage consists inthe release of the vacuum and cooling after the concentrating of the liquor to a consistency. of about 20 even when considerably cooled. By inter-' rupting, however, the concentration at a lower B. degree and cooling, the last quantities of calcium sulfate ((12150 can be eliminated andfiltered off, whereupon the composition is concentrated to the desired consistency, without running risk of having -a. product which acts unfavorably on the tanning process.

As a proof of the product having the property stated, it must be mentioned that the product contains 1% of ashes only, while other products, which are on the market and which are designated as good, contain 12 to 15% of mineral agents, so that the new product has an enormous advantage for the practice.

The quantity of hydrochloric acid and sulfuric acid to be added depends on the kind of raw sulfite liquor employed and must be determined by experiments for each particular case. For instance, for a sulfite liquor having contents of lime of 5.5% CaO 10.5% of concentrated hydrochloric acid (H01) and 8.0% of concentrated sulfuric acid consisting in treating the liquor in a warm state with hydrochloric acid (HCl) and sulfuric acid (H SO and adding thereto potassium chromate (Kr CrO thereby eliminating the remaining lime (Ca), substantially as and for the purpose set forth.

2. A. method of producing tanning compositions from waste sulfite-cellulose liquor, consisting in treating the liquor in a warm state with hydrochloric acid (H01) and sulfuric acid (H 80 adding thereto potassium chromate (Kr GrO thereby eliminating the remaining lime (Ca), concentrating the liquor to about 20 B., cooling it with an admission of air, filtering off the precipitate then falling, and concentrating the liquor to any desired consistency, substan tially as and for the purpose set forth.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

JOHANNES J. GROSS.

Witnesses:

ERNEST L. MUMMENHOFF, IDA CHRIST. HAFERMANN. 

